U.S. Pat. No. 7,423,088 and U.S. 200710149663 teach aromatic trisamide compounds as nucleating agents for thermoplastic polymers.
U.S. 2007/0185247 discloses polypropylene resin containing low loadings of carbon black together with dibenzylidene sorbitol based clarifying agents. The polypropylene articles are taught to have enhanced visual benefits.
MILLAD NX8000 is a commercial clarifying agent for polypropylene available from Milliken, Spartanburg, N.C. It has a bluish tint.
Grimm and Weiser in “Transparent Coloration of Clarified Polypropylene for Packaging Applications”, RETEC Conference: Back to Basics, Cincinnati, Ohio, Sep. 17-19, 2006, pp. 241-253, discusses transparent, colored polypropylene bottles.
The U.S. patents and published applications listed herein are entirely incorporated by reference.
It has been found that polypropylene articles with superior optical properties and/or an increased temperature of crystallization may be prepared where they comprise trisamide nucleating agents together with low levels of polycyclic organic blue, green, magenta, red, yellow, orange or violet pigments.